Is the postganglionic sympathetic neuron zinc-enriched? A stop-flow nerve crush study on rat sciatic nerve.

Axonal transport of endogenous zinc ions in the rat sciatic nerve was studied by a stop-flow/nerve crush technique combined with zinc selenide autometallography (ZnSeAMG) at light and electron microscopic levels. Distinct accumulations of ZnSeAMG grains were detected, in particular proximal but also distal to the crushes, 1.5 h after the operation, and the amounts of zinc ions increased further in the following 3-8 h. Ultrastructurally, ZnSeAMG grains were located predominantly in unmyelinated axons. The data suggest that a subpopulation of sciatic nerve axons contains and transports zinc ions both antero- and retrogradely, indicating that the second neuron in the sympathetic nervous system is zinc enriched (ZEN).